1. Field of the Invention
The present invention relates generally to a roller assembly used for an image forming apparatus. More particularly, the present invention relates to a roller assembly which is capable of reducing driving noise caused by a heating roller and has an improved structure to reduce shaking of the heating roller caused by axial thrusting.
2. Description of the Related Art
Typically, an image forming apparatus has a plurality of roller assemblies to perform various functions and operations. FIGS. 1 and 2 show a heating roller of a fusing unit, which is an example of a roller assembly disposed in the image forming apparatus.
As shown in FIG. 1, a heating roller 10 is rotatably disposed in a frame 1. A bearing 30 is disposed at each end 11 of the heating roller 10 to rotatably support the heating roller 10.
As shown in FIG. 2, the heating roller 10 is assembled with the bearing 30 with an insulating bushing 20 in order to prevent the bearing 30 from being damaged by heat generated by a heater disposed inside the heating roller 10. That is, both ends 11 of the heating roller 10 are inserted and fitted into an inner circumferential surface of the bushing 20, and the bushing 20 is connected with an inner rim 31 of the bearing 30. A roller cover 12 at which a terminal unit is disposed is assembled at both ends of the heating roller 10.
As shown in FIG. 3, a pressure roller 40 is disposed in contact with the heating roller 10 and is rotated by applying pressure to the heating roller 10 in the arrow direction as shown. If the pressure is continuously applied to the bushing 20, it may cause deformation of the bushing 20. A slight change in the dimensions resulting from the deformation of the bushing 20 may degrade the connection force of the ends 11 of the heating roller 10 with the bushing 20. Thus, the heating roller 10 and the bushing 20 may slide with respect to each other, that is, from the connection portion S as shown, and may generate frictional noise.
Furthermore, upon rotation of the heating roller 10, axial thrust is generated (that is, thrust toward the ends 11 in an axial direction) and the heating roller 10 may shake from side to side due to the axial thrust. When the heating roller 10 shakes, the torque required to drive the heating roller 10 increases. If the required torque is too great, the frame 1 may by stressed enough that the frame 1 is deformed.
Accordingly, there is a need for an improved roller assembly for supporting a roller, such as a heating roller, with less noise and with reduced shaking.